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On-board diagnostic (OBD) codes are designed to help mechanics and vehicle owners like you identify possible issues with your vehicle. But before attempting any fixes to resolve the codes retrieved by your scan tool, it’s important to know exactly what they mean.

The P0046 code is one of many error codes that may be set by your vehicle’s primary computer. Read on to learn more about this code’s possible triggers and common symptoms.

What Does the P0046 Code Mean?

Diagnostic trouble code (DTC) P0046 stands for “Turbo/Supercharger Boost Control ‘A’ Circuit Range Performance.” This trouble code is logged when the powertrain control module (PCM) in your vehicle detects a potential problem with the variable geometry turbocharger (VGT) actuator or boost control solenoid.

This code may be set in newer vehicle models equipped with VGT systems when the PCM detects a potential problem with the VGT actuator or its circuit. On older models with traditional turbocharger/supercharger systems, this code may be set if the PCM perceives a possible issue with the performance of the boost control solenoid (also known as the wastegate control valve).

For an in-depth knowledge of turbochargers, superchargers, VGT systems, and the wastegate, you may read our technical discussion here.

The “A” in this trouble code indicates the potential issue is in a certain portion of the system circuit, instead of a specific component or symptom.

Both the turbocharger and the supercharger are forced air induction devices. They forcibly pump air into the engine to increase its power. In modern turbocharged cars, the VGT features internal valves that can be adjusted to alter boost. In older models with a traditional turbocharger/supercharger, the boost is controlled via a wastegate or bypass valve.

The code P0046 may be set if the PCM determines a potential issue with the operation or performance of the VGT actuator or boost control solenoid. Depending on the severity of the problem, other related DTCs may also be stored. Code P0046 is very similar to error codes P0045, P0047, P0048, P0049, and P004A.

supercharged v8 engine
Both the turbocharger and the supercharger are forced air induction devices. They forcibly pump air into the engine to increase its power.

Note: The definition of code P0046 may be different depending on the vehicle manufacturer. Consult the appropriate repair manual or repair database for the exact code definition.

What are the Possible Causes of the P0046 Code?

Here are the most common causes of a P0046 code:

  • Failing boost pressure/turbocharger position sensor
  • Failed boost control solenoid or VGT actuator
  • Faulty turbo/supercharger
  • Wiring issues
  • Damaged PCM

What are the Common Symptoms of the P0046 Code?

You may notice the following symptoms if you drive a vehicle with a stored P0046 trouble code:

  • Check engine light is on
  • Poor engine performance as a result of low boost
  • Detonation and possible engine damage due to overboost

How to Diagnose the P0046 Code

To avoid the possibility of engine damage, code P0046 should be resolved immediately. However, diagnosing this code can be tricky as it has several possible triggers. Always follow the diagnostic procedure specified by your vehicle’s manufacturer. The steps for diagnosing a code P0046 on a Toyota, for instance, may prove different from testing for a code P0046 on a Ford.

Refer to a repair manual for the appropriate diagnostic strategy. If you’re not well-versed in auto repair, it would be best to leave the job to a mechanic.

How to Fix the P0046 Code

P0046 may share similar triggers and symptoms with other engine codes. However, there is no one-size-fits-all fix for these codes. All vehicles are different, so you should always refer to your vehicle’s factory repair information before DIY-ing any repairs.

Code P0046 is a complicated code, so you should always consult a repair manual or repair database before taking any steps to resolve it. If you aren’t confident in your automotive repair skills, it may be best to enlist the help of a professional.

mechanic inspecting turbocharger
If you’re not well-versed in auto repair, it would be best to leave the job to a mechanic.

A Closer Look at Turbochargers and Superchargers

Naturally aspirated engines suffer from a deficiency of efficiency, because they depend on atmospheric pressure to fill the cylinders, and that atmosphere has to clear a lot of obstacles on the way through the air intake system.

A measurement of how much air the engine can process versus how much it can actually get is called “volumetric efficiency” (VE). Most naturally aspirated engines run somewhat less than 100 percent volumetric efficiency, although air intake design helps when the vehicle is in the wind at road speed.

To increase VE above 100 percent, some vehicles have turbochargers or superchargers to force the air into the manifold rather than simply allowing the pistons to draw it in through open valves during the intake stroke.

The Role of the Wastegate

Turbochargers use exhaust flow to spin a “compressor wheel” in the exhaust stream, which is directly connected by a shaft to a turbine wheel that grabs atmosphere and forces it into the engine. The turbocharger shaft spins in bearings or bushings and is somewhat wear prone, since it spins over 100,000 rpm and needs good shaft lubrication via the engine oil gallery.

Superchargers are driven mechanically (belts and pulleys) and don’t spin as rapidly as turbochargers but usually cost a lot more and most have their own oil supply.

Both turbocharging and supercharging tend to heat the air as it is compressed and delivered, and so the air is typically shoved through an intercooler, which is like a radiator with air on the inside rather than coolant, effectively cooling the air charge on its way to the manifold. Cooling the air adds a significant amount of horsepower over compressing the air charge without said cooling.

But both turbochargers and superchargers can and will over-boost an engine, which can be very damaging. To safeguard against this, engineers design turbochargers with a “wastegate,” which allows exhaust gas to bypass the compressor wheel based on intake manifold pressure. If the intake pressure gets too high, the wastegate opens and allows some exhaust gas to take a different path. Supercharger bypass valves perform a similar function, i.e., to prevent over-charging the engine with air.

Initially, a diaphragm with a spring and a hose connected to the intake manifold were used, but with ECM/PCM controls came the need to control the wastegate or supercharger bypass.

Variable Geometry Turbochargers (VGT)

On diesels, variable geometry turbochargers (VGT) became the order of things in the early 2000s. Ford Powerstroke and Chevy Duramax had very similar VGT units with moveable vanes mounted on the turbo housing around the outside of the compressor wheel that allowed the turbo to spin at different speeds depending on engine speed and load. VGT units don’t require a wastegate because the turbo output is controlled differently.

Dodge Cummins engines opted for a different type of VGT, but all three of these platforms use a solenoid and sometimes oil pressure devices to control turbocharging. That being said, you won’t find a P0046 code on all these diesel engines. When you do receive the code, it typically means there’s a problem with the turbo actuator that controls turbo output. The ECM/PCM uses either pressure or mechanical feedback to determine if the turbo actuator system is working right.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic.

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